Chapter 1

What is a chemical? A chemical is any substance that has a definite composition. Chemical changes and reactions take place all the time.

Examples of chemical reactions: Photosynthesis –turns CO2 and sunlight into food and oxygen Rusting of metal Burning a match

objectives Distinguish between elements and compounds Distinguish between pure substances and mixtures Classify mixtures as homogeneous or heterogeneous Explain the difference between mixtures and compounds

Classifying matter Everything around you is made up of ___________. All matter is composed of ___________.

Pure substances Every pure substance has characteristic __________ that can be used to identify it. These properties can be ____________ or chemical. There are two types of pure substances, ____________ and ____________.

Elements Elements are pure substances that contain only one kind of atom. Copper and bromine are elements. The __________ __________ is an organized list of all the elements.

Molecules A ____________ usually consists of two or more atoms combined in a definite ratio. Examples H2 F2 Cl2

Compounds Pure substances that are not ____________ are compounds. Compounds are composed of more than one kind of atom.

Classify the following as a Pure substance, compound, or element Classify the following as a Pure substance, compound, or element. Choose all that apply CO2 F2 C6H12O6 SO4 C9H8O4 H2O Fe Ag

Mixtures A mixture is a sample of matter that contains two or more pure substances ___________ combined. Most kinds of foods are mixtures except _________ and _________. Air is a mixture Water (is, is not) a mixture

Classifying mixtures In homogeneous mixtures the pure substances that are combined are distributed uniformly throughout the entire mixture. Gasoline Syrup Air There different components cannot be seen

Continued… In heterogeneous mixtures, the substances are not evenly mixed Italian dressing Chocolate chip cookies Salad Muddy water

Review What is the difference between an element and a compound? What’s the difference between pure substances and mixtures? What’s the difference between mixtures and compounds?